The present invention relates to carriers used in the test, assembly and packaging of semiconductors and other microelectronic devices.
In the manufacture of semiconductor products, it is often necessary to perform various die tests and other operations on the semiconductor die after they have been diced from the wafer. In order to perform these operations on the microscopic scales necessary, the fixtures used to hold the semiconductor die must be of very high precision. Conventionally, a semiconductor die is bonded to a flat substrate (often referred to as a coupon) within a very precise tolerance referenced to the edges of the coupon. The coupon is then loaded into an aperture in a multi-apertured rack for further processing. A conventional rack type fixture known as an AUER boat comprises a rack frame approximately 5 inches by 12 inches across containing typically from 5 to 50 apertures depending on the size of the coupons being handled. Each aperture in the rack is manufactured within a close tolerance relative to the size of the coupon such that the position of the die relative to the frame of the boat is known within sufficient tolerance to carry out the intended processing operation (e.g. probing, wire bonding, etc.). Conventionally, the frame of the AUER boat includes a plurality of small holes called xe2x80x9cfidicualsxe2x80x9d, which are a precise distance from the center of the adjacent aperture. The fidicuals are used by the processing equipment as a reference to align the processing equipment to the aperture (and therefore to the die) prior to conducting the processing operation.
Because of the inherent tolerance limitations in the precision stamping process used to manufacture the frames, typically no better than plus or minus 0.005 inches from aperture to aperture, the processing equipment using such frames must align itself with each individual aperture before the process operation can take place. The necessity of aligning the processing equipment with each individual aperture has a dilitarious effect on the maximum throughput of the processing equipment. Other methods of manufacturing the frame such as milling or EDM could yield a frame within tighter tolerances but only at exorbitant costs. Accordingly, what is needed is a method of precision stamping multi-apertured process carrier frames within ultra-precise tolerances such that the semiconductor processing equipment can align itself once with the frame and conduct the processing operations on all the die carried by the frame without the necessity of realigning itself to each individual aperture.
The present invention comprises an ultra precision stamped process carrier frame for use in the manufacture of semiconductors, liquid crystal displays, micromachines and other microelectronic devices. According to a preferred embodiment of the process carrier, each of the coupon carrying apertures in the frame has a serrated side wall comprising a plurality of fingers extending into the aperture. The tips of the fingers define the aperture that registers the semiconductor coupon. Because only the tips of the fingers are shaved in the final process step, the registration apertures can be held to a tighter tolerance relative to the fidicual than is possible when the entire side wall of the aperture is punched.
According to a preferred method of manufacturing the precision carrier, the rough aperture for the coupon is initially stamped in the carrier frame such that the fingers extend into the aperture further than the finished dimension (i.e. the aperture is undersized). Since the initial act of opening the apertures in the frame will necessarily relieve internal stresses in the material, the frame will inherently become warped. Therefore, the unfinished carrier plate is preferably processed through a conventional flattening machine to restore the original flatness (at the cost of some elongation and other distortion of the unfinished apertures). The mechanically and or thermally stress relieved and flattened process carrier plate is then subjected to an additional die punching operation in which the tips of the fingers of all of the apertures in the plate are shaved to the finished dimension and the fidicual holes punched in the plate all in one simultaneous operation. Since all of the apertures in the plate are finished to the final dimension simultaneously with each other and with the punching of the fidicuals, the aperture-to-aperture tolerance as well as the aperture-to-fidicual tolerance is limited only by the precision to which the punch itself is manufactured. Thus, tolerances of plus or minus 0.001 inch or better can be achieved across the entire frame. The finished stamping process may be carried out at a temperature other than ambiant in order to further increase precision, that is, if the customer user point carrier temperature is greater than ambiant, the finished stamping process may be carried out at the user point carrier temperature in order to ensure that the process carrier plate does not go out of tolerance as the result of the thermal coefficient of expansion of the plate material. Additionally, performing the finished stamping operation at above or below the customer user point carrier temperature may permit the operation to be xe2x80x9ctweekedxe2x80x9d to allow the thermal coefficient of expansion of the material to grow or shrink the part as necessary to meet customer requirements.